# -*- coding: utf-8 -*-
from sys import stdin
import math
# 0 0 1 1

A = list(map(float, stdin.readline().split()))
x1, y1, x2, y2 = A[0], A[1], A[2], A[3]

distance = math.sqrt(math.pow(x2-x1, 2) + math.pow(y2-y1,2))
print(format(distance,'.8f'))
 from sys import stdin import math math A = list(map(float, stdin.readline().split())) A list(map(float, stdin.readline().split())) list map(float, stdin.readline().split()) map float stdin.readline().split() stdin.readline().split stdin.readline() stdin.readline stdin readline split x1, y1, x2, y2 = A[0], A[1], A[2], A[3] x1 A[0] A 0 y1 A[1] A 1 x2 A[2] A 2 y2 A[3] A 3 distance = math.sqrt(math.pow(x2-x1, 2) + math.pow(y2-y1,2)) distance math.sqrt(math.pow(x2-x1, 2) + math.pow(y2-y1,2)) math.sqrt math sqrt math.pow(x2-x1, 2) + math.pow(y2-y1,2) math.pow(x2-x1, 2) math.pow math pow x2-x1 x2 x1 2 math.pow(y2-y1,2) math.pow math pow y2-y1 y2 y1 2 print(format(distance,'.8f')) print format(distance,'.8f') format distance '.8f' y2 = A[0], A[1], A[2], A[3] A[3] y2 A = list(map(float, stdin.readline().split())) list(map(float, stdin.readline().split())) A x2, y2 = A[0], A[1], A[2], A[3] A[2] x2 x1, y1, x2, y2 = A[0], A[1], A[2], A[3] A[0] x1 distance = math.sqrt(math.pow(x2-x1, 2) + math.pow(y2-y1,2)) math.sqrt(math.pow(x2-x1, 2) + math.pow(y2-y1,2)) distance y1, x2, y2 = A[0], A[1], A[2], A[3] A[1] y1
# -*- coding: utf-8 -*-
from sys import stdin
import math
# 0 0 1 1

A = list(map(float, stdin.readline().split()))
x1, y1, x2, y2 = A[0], A[1], A[2], A[3]

distance = math.sqrt(math.pow(x2-x1, 2) + math.pow(y2-y1,2))
print(format(distance,'.8f'))

